Photon ring multi-user distribution system for a soft X-ray SASE FEL laboratory

Although the soft X-ray photon beam from a SASE FEL undulator is in principle a single user tool, just like an optical laser, an optical distribution system based on multifacet reflectors can provide efficient ways to generate a multi-user facility - very similar to present day synchrotron radiation facilities. Multifacet reflectors involve multiple reflections from a series of plane mirrors. They can be repeated a number of times to form a complete ring. In principle, a few tens of beam lines with different experiments can be served by a single FEL source. Using movable mirrors in each photon ring cell it is possible to quickly switch the FEL photon beam from one experiment to the other, thus providing simultaneous multi-user capability. (orig.)